一种基于CPLD的脉冲功放过脉宽、过占空比检测方法

介绍了一种基于CPLD的脉冲功放过脉宽、过占空比检测方法。该方法能够实时精确地获取功放脉冲调制信号或射频检波信号的脉宽和周期数据,得到过脉宽、过占空比保护信号。相比传统检测方法,具有精度高、实时性强、执行效率高、抗干扰能力强、环境适应性好、扩展能力强等优点。

一种带上电时序控制及过脉宽保护功能的大功率调制电路研究

大功率脉冲调制电路根据雷达系统所需脉冲宽度及重频将连续电压信号调制为脉冲工作电压,可以改善GaN功率器件的效率与可靠性。为了提升调制发射脉冲信号的上升下降沿速度,提高大功率调制电路可靠性,提出一种新型带上电时序控制及过脉宽保护功能的大功率调制电路,该电路包括上电时序控制电路、过脉宽保护电路、大功率调制电路。通过对电路进行理论分析,给出详细参数并计算该电路参数,并对关键参数进行仿真及实测验证,该电路具有调制电压高,上升下降沿速度快等特点。经过测试验证,调制电压最高100 V,调制频率最高可达500 KHz,峰值工作电流超过20 A,上升沿、下降沿小于30 ns。具有广阔的应用前景。

《徐霞客游记》词语札记

本文选取《徐霞客游记》中的"过脉"、"乖/蔴拐"和"肥"几个词语,运用现代语言学的词汇考释方法加以解释。认为"过脉"是堪舆学常用语,有名词和动词两种用法;"乖"的语源是苗瑶语,"蔴拐"的所指与"乖"一致,是一个合璧词;"肥"因形讹而误,"索肥"的正字为"索(貝巴)",意义为"索取买路钱"。

测试台中自制数字式定时器的实现与应用

首先阐述了数字式定时器在回旋管测试台系统中的组成框图及其重要性。研究并利用数字处理器的外部总线接口实现了对可编程器件的连接控制,并重点叙述了总线的读写时序关系和有关接口模块的实现代码。在系统设计中考虑了过脉宽和过占空比现象对设备的影响并给出了有效解决方案。借助人机界面设备可以很方便地实现对定时器的输出脉冲宽度和重复频率的设置,同时还解决了参数记忆保存的问题。基于数据总线实现了对嵌入式芯片的控制,该方式对普通自制式仪表设计具有借鉴意义。

Microstructure and depositional mechanism of Ni-P coatings with nano-ceria particles by pulse electrodeposition

Nano-CeO2 （RE） particles were co-deposited into Ni-P binary composite coatings by applying pulse current （PC） under ultrasonic （U） field. Morphology, chemical content and crystal microstructure were characterized by environmental scanning electron microscopy （E-SEM） with energy dispersive X-ray analysis （EDXA）, XRD diffractometry and transmission electron microscopy （TEM）. Experimental results show that Ni-P coating reinforced with 15g/L nano-CeO2, in amorphous state and with compact structure, can be improved in the microhardness from HV0.2580 to HV0.2780 by annealing at 600 °C for 2 h. The highest content of codeposited Ce and deposition rate can reach 2.3% and 68 μm/h, respectively. Furthermore, the effect of RE adsorption and pulse overpotential on depositional mechanism was investigated. n-CeO2 particles or Ce4＋ ions with strong adsorption capacity acted as the catalytic nucleus to improve densification effectively. During annealing at 600 °C for 2 h, n-CeO2 particles will uniformly adsorb on crystal grain to preferentially pad and heal up gaps of cracking Ni boundaries, promoting dispersion strengthening with refiner-grained structure.

Welding characteristics of AZ31B magnesium alloy using DC-PMIG welding

Direct current pulsed metal inert-gas （DC-PMIG） welding was carried out on AZ31B magnesium alloy to obtain continuous welding joints of 3 mm and 8 mm thickness with 1.6 mm diameter of filler wire. The behavior and mechanism of metal transfer, the parameter ranges of stable welding process, the microstructure and mechanical properties of magnesium alloy were investigated. The results show that the metal transfer form of magnesium alloy using DC-PMIG welding is realized in modes of globular transfer, projected transfer and spray transfer. Welding spatter with a large size will be produced in the mode of globular transfer, and high-quality joints with few spatters can be obtained in the mode of projected transfer and spray transfer when the linear energy of filler wire is 242-27l J/cm, droplet diameter is 1.6-0.9 mm tensile strength of weld beads is 94.2% of that of base metals. and transition frequency is 30-69 Hz. The average ultimate

Grain refinement of as-cast superalloy IN718 under action of low voltage pulsed magnetic field

The grain refinement of superalloy IN718 under the action of low voltage pulsed magnetic field was investigated. The experimental results show that fine equiaxed grains are acquired under the action of low voltage pulsed magnetic field. The refinement effect of the pulsed magnetic field is affected by the melt cooling rate and superheating. The decrease of cooling rate and superheating enhance the refinement effect of the low voltage pulsed magnetic field. The magnetic force and the melt flow during solidification are modeled and simulated to reveal the grain refinement mechanism. It is considered that the melt convection caused by the pulsed magnetic field, as well as cooling rate and superheating contributes to the refinement of solidified grains.

Influence of continuous veno-venous hemofiltration on the course of acute pancreatitis

AIM： To investigate whether continuous veno-venous hemofiltration （CVVH） in different filtration rate to eliminate cytokines would result in different efficiency in acute pancreatitis, whether the saturation time of filter membrane was related to different filtration rate, and whether the onset time of CWH could influence the survival of acute pancreatitis. METHODS： Thirty-seven patients were classified into four groups randomly. Group 1 underwent low-volume CVVH within 48 h of the onset of abdominal pain （early CVVH, n = 9）. Group 2 received low-volume CVVH after 96 h of the onset of abdominal pain （late CVVH, n= 10）. Group 3 underwent high-volume CVVH within 48 h of the onset of abdominal pain （early CVVH, n = 9）. Group 4 received high-volume CVVH after 96 h of theonset of abdominal pain （late CVVH, n = 9）. CVVH was sustained for at least 72 h. Blood was taken before hemofiltration, and ultrafiltrate was collected at the start of CVVH and every 12 h during CVVH period for the purpose of measuring the concentrations of TNF-α, IL-1β and IL-6. The concentrations of TNF-α, IL-1β and IL-6 were measured by swine-specific ELISA. The Solartron 1 255 B frequency response analyzer （British） was used to observe the resistance of filter membrane. RESULTS： The survival rate had a significant difference （94.44% vs68.42%, P〈0.01） high-volume and low-volume CVVH patients. The survival rate had also a significant difference （88.89% vs 73.68%, P〈0.05） between early and late CVVH patients. The hemodynamic deterioration （MAP, HR, CVP） was less severe in groups 4 and 1 bhan that in group 2, and in group 3 than in group 4. The adsorptive saturation time of filters membranes was 120-180 min if the filtration rate was 1 000-4 000 mL/h. After the first, second and third new hemofilters were changed, serum TNF-α concentrations had a negative correlationwith resistance （r： -0.91, -0.89, and -0.86, respectively in group 1; -0.89, -0.85, and -0.76, respectively in group 2; -0.88, -0.92, and -0.82, respectively in group 3; -0.84, -0.87, and -0.79, respectively in group 4）. The decreasing extent of TNF-α, IL-1β and IL-6 was significantly different between group 3 and group I （TNF-α P〈0.05, IL-1β P〈0.05, IL-6 P〈0.01）, between group 4 and group 2 （TNF-α P〈0.05, IL-1β P〈0.05, IL-6 P〈0.01）, between group 1 and group 2 （TNF-α P〈0.05, IL-1β P〈0.05, IL-6 P〈0.05）, and between group 3 and group 4 （TNF-α P〈0.01, IL-1β P〈0.01, IL-6 P〈0.05）, respectively during CVVH period. The decreasing extent of TNF-α and IL-1β was also significantly different between survival patients and dead patients （TNF-α P〈0.05, IL-1β P〈0.05）. In survival patients, serum concentration of TNF-α and IL-1β decreased more significantly than that in dead patients. CONCLUSION： High-volume and early CWH improve hemodynamic deterioration and survival in acute pancreatitis patients. High-volume CVVH can eliminate cytokines more effidently than low-volume CVVH. The survival rate is related to the decrease extent of TNF-α and IL-1β. The adsorptive saturation time of filter membranes are different under different filtration rate condition. The filter should be changed timely once filter membrane adsorption is saturated.

Optimization of Nozzle Design for Pulse Cleaning of Ceramic Filter

The experimental study was carried out to optimize the nozzle shape and dimension for the pulse cleaning of a ceramic filter candle. A bench scale unit of ceramic filter consisting of four commercial filter elements was used to measure the traces of the transient pressure around the nozzle and the overpressure in the filter cavity during the pulse-jet injection of pulse gas. Overpressure in the filter cavity is related to the pulse cleaning force. Nozzle design is concerned to increase the overpressure at the open end of filter element of pulse cleaning inlet, as well as to minimize the consumption of pulse gas. Convergent nozzle induces more secondary flow and generates higher pulse cleaning effect than straight nozzle. Nozzles of different convergent ratio （ratio of outlet to inlet diameter of nozzle） by changing the convergent angle and height were tested. The outlet diameter of convergent nozzle seriously influences the cleaning effect. The optimum convergent ratio increases with the increase of pulse gas pressure The nozzle position （distance of nozzle tip from the open end of filter inlet） is also important to decide the nozzle dimension. Nozzle of large outlet diameter accepts high pressure of pulse gas to provide large overpressure in the filter cavity of top position by applying long distance.

CFD analysis of sound pressure in tank gun muzzle silencer

The high pressure waves generated due to muzzle blast flow of tank gun during firing is a critical issue to examine. The impulsive noise from the gun has various negative effects such as damage of human bodies, damage of structures, creating an environmental, social problem and also military problems such as exposure of location of troops. This high pressure impulsive sound, generated during the blast flow, was studied and attenuated. An axisymmetric computational domain was constructed by employing Spalart Allmaras turbulence model. Approximately 90% of pressure and 20 dB of sound level are reduced due to the use of the three baffle silencer at the muzzle end of the gun barrel, in comparison with the tank gun without silencer. Also, the sound pressure level at different points in the ambient region shows the same attenuation in results. This study will be helpful to understand the blast wave characteristics and also to get a good idea to design silencer for large caliber weapon system.

Image Analysis on Detachment Process of Dust Cake on Ceramic Candle Filter

Based on the analysis of high-speed video images, the detachment behavior of dust cake from the ceramic candle filter surface during pulse cleaning process is investigated. The influences of the dust cake loading,the reservoir pressure, and the filtration velocity on the cleaning effectiveness are analyzed. Experimental results show that there exists an optimum dust cake thickness for pulse-cleaning process. For thin dust cake, the patchy cleaning exists and the cleaning efficiency is low; if the dust cake is too thick, the pressure drop across the dust cake becomes higher and a higher reservoir pressure may be needed. At the same time there also exists an optimum reservoir pressure for a given filtration condition.

The importance of depression and alcohol use in coronary artery bypass graft surgery patients：risk factors for delirium and poorer quality of life

ObjectiveToinvestigate whether depression, anxiety and stress increase the risk for delirium and poor quality of life （QOL） after co-ronary artery bypass （CABG） surgery.MethodsA total of 180 CABG patients （mean age of 63.5 ± 10.1 years, 82.2% males） completed baseline and postoperative self-report questionnaires to assess distress and QOL. Incident delirium was diagnosed postoperatively with a structured clinical interview and patients were monitored every day post-operatively for confusion and disturbance in consciousness.Results Delirium developed in 63 persons （35% of sample）. After adjustment for covariates, delirium was significantly associated with depression [odds ratio （OR）： 1.08; 95% confidence interval （CI）： 1.03-1.13,P = 0.003], anxiety （OR： 1.07; 95% CI： 1.02-1.13,P= 0.01） and stress （OR： 1.05; 95% CI： 1.00-1.09,P= 0.03）. Preoperative depression scores were associated with poorer QOL including bodily pain （β =-0.39,P = 0.013）, vitality （β=-0.32,P = 0.020）, social functioning （β=-0.51,P≤0.001）, emotional role function （β=-0.44,P = 0.003） and general health （β=-0.33,P = 0.038）. Among the covariates, harmful levels of alcohol use was consistently associated with poorer QOL.Conclusions Depression and harmful levels of alcohol use were consistently associated with poorer QOL whereas depression, anxiety and stress were associated with delirium risk. These findings point to further research examining depression and harmful levels of alcohol use in coronary heart disease populations undergoing coronary revascularization.

Cost-effectiveness analysis of early veno-venous hemofiltration for severe acute pancreatitis in China

AIM： To determine the most cost-effective hemofiltration modality for early management of severe acute pancreatitis （SAP） in China. METHODS： We carried out a search of Pub-Medline and Chinese Biomedical Disk database. Controlled clinical trials on Chinese population were included in the analysis. The four decision branches that were analyzed were： continuous or long-term veno-venous hemofiltration （CVVH/LVVH）, short-term veno-venous hemofiltration （SVVH）, SVVH plus peritoneal dialysis （PD）, and non-hemofiltration control group. The effectiveness of the technique was determined by survival rate, complications prevention and surgery preservation. The total cost of hospitalization was also assessed. RESULTS： The SVVH only technique was the least costly modality, $5809 （44449 RMB）, and was selected as the baseline treatment modality. SVVH only arm achieved the lowest C/E ratio in terms of overall survival, complications prevention and surgery preservation. In incremental cost-effectiveness analysis, the CWH/ LVVH only and the control arms were inferior to other techniques. Sensitivity analysis showed SVVH only and SVVH plus PD arms overlapped in C/survival ratio. CONCLUSION： The role of early veno-venous hemofiltration as an alternative therapy for SAP remains controversial. However, we propose that early use of short-term high-volume veno-venous hemofiltration would have a beneficial impact on the management of SAP.

Off-pump coronary artery bypass grafting versus optimal medical therapy alone：effectiveness of incomplete revascularization in high risk patients

BackgroundGeriatric patients with multivessel coronary artery disease （CAD） are a challenging group to treat; these cases elicit dis-cussion within heart teams regarding the actual benefit of undertaking major surgery on these patients and often lead to abandon the surgical option. Percutaneous procedures represent an important option, but coronary anatomy may be unfavorable. Off-pump coronary artery bypass （OPCAB） provides good quality graft on left anterior descending （LAD） without exposing the patient to cardiopulmonary bypass, and might be the ideal choice in patients with multiple comorbidities, not eligible to percutaneous or on-pump procedures. The objective of this study was to compare survival during a mid-term follow-up in high-risk patients with no percutaneous alternative, either treated with OPCAB or discharged in medical therapy.MethodsWe retrospectively evaluated from June 2008 to June 2013, 83 high-risk patients with multivessel CAD were included： 42 were treated with incomplete off-pump revascularization using left internal mammary artery （LIMA） on LAD; 41 were discharged in optimal medical therapy （OMT）, having refused surgery. Follow-up ended in March 2015, with a telephonic interview. Primary endpoint was survival from all-cause mortality; secondary endpoints were survival from cardiac-related mortality and freedom from non-fatal major adverse cardiac events （MACEs）.ResultsDuring follow up, 11 deaths in OPCAB group and 27 deaths in OMT group occurred. Death was due to cardiac factors in 6 and 15 patients, respectively. MACEs were observed in 6 patients in OPCAB group and in 4 patients in OMT group. With regards to survival from all-cause mortality, patients who underwent OPCAB survived more than those dis-charged in OMT （Log Rank ＆lt; 0.001）, and OMT group carries a propensity score-adjusted hazard ratio of 3.862 （P ＆lt; 0.001）. With regards to survival from cardiac-related events, patients who underwent OPCAB survived more than those discharged in OMT （Log Rank = 0.002）, and OMT group carries a propensity score-adjusted hazard ratio of 3.663 （P = 0.010）. There is no statistically significant difference concerning freedom from MACEs （Log Rank = 0.273）.ConclusionsFor high-risk patients with multivessel CAD, not eligible to on-pump complete revascularization surgery or percutaneous procedures, incomplete revascularization with OPCAB LIMA-on-LAD offers benefits in survival when compared to OMT alone.

Numerical Analysis of Flow Field in Ceramic Filter During Pulse Cleaning

In the commercial utilization of rigid ceramic filters, the performance of pulse cleaning has crucial effects on the long-term stable operation. In order to get a clear insight into the nature of this cleaning process and provide a solid basis for industrial applications, the flow in ceramic candle filter was investigated. The flow in the pulse-jetspace and inside the ceramic candle is regarded as two- dimensional, unsteady, compressible flow, and numerical simulation is carried out by computational fluid dynamics. The numerical predictions of flow field are in good agreement with the experimental measurements. Effects of the candle diameter, the separation distance between the nozzle and the candle injector and the length of the candle on the flowfield have been numerically analyzed to provide the basis for the optimum design of the pulse cleaning system.

Science Letters:Cellular growth under hydrostatic pressure using bovine aortic EC-SMC co-cultured ePTFE vascular graft

High blood pressure (hypertension) is implicated in the development of atherosclerosis. Blood vessels are constantly subjected to stretch due to blood pressure and changes in stretch usually instigate adaptive vascular remodeling, including abnormal growth and proliferation of vascular smooth muscle cells (VSMCs) as well as extracellular matrix (ECM). In this experiment, we used bovine aortic endothelial cells and smooth muscle cells (EC-SMC) co-cultured ePTFE vascular grafts subjected to normal atmospheric pressure (as a control), and 100 mmHg hydrostatic pressure for 7 d. The increase of cell layer thickness was observed. When measured, the cell layer thickness increased by 116.2%. The increase of collagen (Type Ⅳ)synthesis was also observed in the immunohistochemistry assay. When stained with toluidine blue, the cells showed metachromatic phenomenon.

Pretreatment with adenosine and adenosine A1 receptor agonist protects against intestinal ischemia-reperfusion injury in rat

AIM： To examine the effects of adenosine and A1 receptor activation on reperfusion-induced small intestinal injury. METHODS： Rats were randomized into groups with sham operation, ischemia and reperfusion, and systemic treatments with either adenosine or 2-chloro-N^6-cyclopentyladenosine, A1 receptor agonist or 8-cyclopentyl- 1,3-clipropylxanthine, A1 receptor antagonist, plus adenosine before ischemia. Following reperfusion, contractions of ileum segments in response to KCl, carbachol and substance P were recorded. Tissue myeloperoxidase,malondialdehyde, and reduced glutathione levels were measured. RESULTS： Ischemia significantly decreased both contraction and reduced glutathione level which were ameliorated by adenosine and agonist administration. Treatment also decreased neutrophil infiltration and membrane lipid peroxidation. Beneficial effects of adenosine were abolished by pretreatment with A1 receptor antagonist. CONCLUSION： The data suggest that adenosine and A1 receptor stimulation attenuate ischemic intestinal injury via decreasing oxidative stress, lowering neutrophil infiltration, and increasing reduced glutathione content.

Impulse Control Problem of Partially Observed Diffusion Processes

The authors investigate the problem of impulse control of a partially observed diffusion process. The authors study the impulse control of Zakai type equations. The associated value function is characterized as the only viscosity solution of the corresponding quasi-variational inequality. The authors show the optimal cost function for the problem with incomplete information can be approximated by a sequence of value functions of the previous type.

Postoperative atrial fibrillation and vitamin D

To the Editor I have read the article entitled ＂Predictors of new-onset atrial fibrillation in elderly patients with coronary artery disease after coronary artery bypass graft＂ by Anatol＇evna, et al. with great interest. The investigators reported that independent predictors of postoperative atrial fibrillation （POAF） after coronary artery bypass graft （CABG） in eld- erly patients were left atrium dimension （LA） and the in- creased postoperative concentration of Interleukin （IL）-6, IL-8 and superoxide dismutase.

Soliton—Like Pulses in Vertical Granular Chain Under Gravity：Particle—Like or Wave—Like

We numerically study the propagation, reflection and collision of soliton-like pulses in the vertical granular chain under gravity. For the pure granular chain system, during the propagation and reflection processes at the fixed end, it behaves like a particle. When it is reflected at the free end, it behaves as neither particle-like nor wave-like. When the strengths of the two colliding soliton-like pulses are close, they collide just like particles. When their strengths are greatly different, they collide just like waves. For the soliton behavior in the collision process, from particle-like to wave-like, there is a critical value for the ratio of the strengths of the two initial pulses. For the two-layer granular chain, if the mass of the grains in the second layer is less than that in the first layer, the soliton-like pulse in the first layer usually excites about soliton-like pulses in the second layer.